atlantic jet

7/28/2019 Atlantic Jet

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Atlantic Jet:

Stability of jet core


2/39

Thermal winds between 930 and

430 hpa


3/39

Look at cross sections where the

baroclinicity is greatest those

positions are


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Velocity in Cross section-

Northern Hemisphere


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Temperature in cross section-

700hpa


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Modern Stability


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Modern Stability


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LGM Stability


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LGM Stability


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Mid Atlantic Jet Look at jet stability at location of greatest barotropic shear at 800 hpa


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Mid Atlantic Jet Also consider vorticity gradient


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Find location of max shear and

vorticity gradient in LGM

Minnimum vorticity gradient

Maximum Velocity Shear


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Cross sections of zonal velocity at

location of maximum velocity shear


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Mid atlantic modern stability-

structure of eddy


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Mid atlantic modern stability-

Growth by layer


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Mid atlantic LGM stability-

Structure of Eddy


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Mid atlantic LGM stability- Growth

by layer


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Seeding the mid-atlantic

Initialize the mid atlantic mean state jet with

normal modes from the Western Atlantic

Look at growth rates instantaneously whichcan be determined by projection of

tendency onto stream function or finite

differencing of the standard deviation ofperturbation time series (equivalent results)


19/39

Seeding the mid-atlanticModern normal mode growth rates are

Western Atlantic = 3.7 * 10 ^ -6Mid Atlantic = 2.6 *10 ^ -6


20/39

Seeding the mid-atlanticLGM normal mode growth rates are

Western Atlantic = 5.9 * 10 ^ -6Mid Atlantic = 4.65 *10 ^ -6


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2d Atlantic jet -LGM Define a domain over which the thermal wind between

900 hPa and 400 hPa is above a threshold value.

LGM


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2d Atlantic Jet - LGM Transition between this 2d zonal velocity and the zonal mean zonal

velocity, on a rectangular, singly periodic domain


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2d Atlantic Jet - LGM The jet has horizontal divergence which is nearly compensated for by vertical

divergence

Match is not exact because the conversion from the sphere to the rectangle has ageometric factor--- IS THERE SOMETHING ELSE HERE?

LOWER LEVEL


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2d Atlantic Jet- LGM The jet has horizontal divergence which is nearly compensated for by vertical

divergence


UPPER LEVEL


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2d Atlantic Jet - LGM Find the meridional velocity which makes the jet non-divergent and has no flow

through top and bottom boundary

-Doing both is impossible because there is vertical divergence and the conversionfrom the sphere to the rectangle has a geometric factor

LOWER LEVEL


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2d Atlantic Jet - LGM Find the meridional velocity which makes the jet non-divergent and has no flow



UPPER LEVEL


27/39

2d Atlantic Jet - LGM Eddies after 45 day integration


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2d Atlantic Jet - LGM Eddy growth in upper layer- growth rate 3.5 *10^-6 Smaller than zonally invariant

case

E fold in 3.3 days

0 0.5 1 1.5 2 2.5 3

x 106

2

4

6

8

10

12

14

layer 1 data

layer 1 fit s lope = 3.4849e-006layer 3 data

layer 3 fit slope =3.4958e-006

spatial growth == 3.5134e-006+3.537e-006i


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2d Atlantic Jet - LGM Size of eddies by region left half vs right half and middle half vs edge half

0 0.5 1 1.5 2 2.5 3

x 106

0.5

0.6

0.7

0.8

0.9

1

1.1

1.2

1.3

1.4

1.5Ratio of eddy activity in different parts of the domain as a function of time

time (hours)

ration

ofstandard

deviations

Layer 1 ratio of left to right

Layer 1ratio of middle to edge


Layer 3 ratio of middle to edge


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2d Atlantic Jet - LGM

Growth by region Projection of tendency onto streamfunction


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2d Atlantic jet - MODERN Define a domain over which the thermal wind between

900 hPa and 400 hPa is above a threshold value.

MODERNMODERN


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2d Atlantic Jet- MODERN Transition between this 2d zonal velocity and the zonal mean zonal

velocity, on a rectangular, singly periodic domain


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2d Atlantic Jet- MODERN The jet has horizontal divergence which is nearly compensated for by vertical

divergence


LOWER LEVEL


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2d Atlantic Jet- MODERN The jet has horizontal divergence which is nearly compensated for by vertical

divergence


UPPER LEVEL


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2d Atlantic Jet - MODERN Find the meridional velocity which makes the jet non-divergent and has no flow



LOWER LEVEL


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2d Atlantic Jet- MODERN Find the meridional velocity which makes the jet non-divergent and has no flow



UPPER LEVEL


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2d Atlantic Jet-MODERN Eddies after 25 day integration- vertical tilt = 53 degrees


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2d Atlantic Jet - MODERN Eddy growth in upper layer- growth rate 2.8 *10^-6 Smaller than zonally invariant cases

E fold in 4 days-

_-Pulses between upper and lower level- NUMERICAL instability?

0 1 2 3 4 5 6

x 106

0

2

4

6

8

10

12

14

16

18

layer 1 data

layer 1 fit slope = 2.8619e-006

layer 3 data

layer 3 fit slope =2.8497e-006

spatial growth == 2.3347e-006+2.7205e-006i


39/39

2d Atlantic Jet - MODERN The eddy size and growth by region oscillates in time

G h b i Edd i b i

0 1 2 3 4 5 6

x 106

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2Ratio of eddy activity in different parts of the domain as a function of time

time (hours)

ration

ofstandard

deviations


Layer 1ratio of middle to edge


Layer 3 ratio of middle to edge

atlantic jet

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